The present invention relates to a fixing apparatus for use in a copying machine, a printer and a facsimile machine, and in particular, to a fixing apparatus capable of conducting quick start fixing.
Heretofore, as a fixing unit used for a copying machine, a printer and a facsimile machine, those of a heat roller fixing system have been used widely for a low speed machine up to a high speed machine and for machines for monochromatic images and full-color images, as a stable and highly sophisticated one.
In the fixing unit of a conventional heat roller fixing system, however, when heating a transfer material and toner, there has been a problem that it is disadvantageous for energy conservation because of poor effect of energy conservation because a fixing roller with great heat capacity needs to be heated, and a long time is required for warming a fixing unit in the course of printing, resulting in a long printing time (warming-up time).
A fixing unit of a film fixing system wherein a film (heat fixing film) is used to solve the above-mentioned problem, a heat roller is changed to a heat fixing film having an ultimate thickness and low heat capacity, heat conduction efficiency is extremely improved by bringing the temperature-controlled heater (ceramic heater) into direct contact with the heat fixing film, and thereby, energy conservation and quick start which hardly requires warming-up time are achieved, and a color image forming apparatus employing the fixing unit of a film fixing system, have been proposed, and they are used recently.
Fixing methods wherein a light transmissive base member representing a variation of the heat roller is used as a heat ray fixing roller (a roller member for heat ray fixing), and heat ray emitted from a halogen lamp (heat ray irradiating means) provided inside is projected on toner to heat and fix the toner and quick start requiring no warming-up time is achieved, are disclosed in TOKKAISHO Nos. 52-106741, 57-82240, 57-102736 and 57-102741. Further, a fixing method wherein a heat ray fixing roller (a roller member for heat ray fixing) is constructed by providing a light absorbing layer on an outer periphery of a light transmissive base member, heat ray emitted from a halogen lamp (heat ray irradiating means) provided inside of the light transmissive base member is absorbed by the light absorbing layer provided on the outer periphery of the light transmissive base member and a toner image is fixed by heat of the light absorbing layer, is disclosed in TOKKAISHO Nos. 59-65867.
However, in the method disclosed in TAKKAISHO No. 52-106741 wherein toner is irradiated by a heat ray emitted from a halogen lamp (heat ray irradiation means) is applied to toner through a light transmissive base member to heat and fix the toner, and in the method disclosed in TAKKAISHO No. 59-65867 wherein a heat ray fixing roller (heat ray fixing roller member) is structured by providing a light absorbing layer (heat ray absorbing layer) on an outer circumferential surface of a light transmissive base member, and a heat ray emitted from a halogen lamp (heat ray irradiation means) is applied to the light absorbing layer through the light transmissive base member so that toner may be fixed by heat of the light absorbing layer, there are achieved both energy conservation and quick start with decreased warming-up time. However, in the heat ray fixing roller member, a cylindrical glass member is mainly used as a material of the light transmissive base member in the heat ray fixing roller member. Therefore, when a flange member into which a bearing member (bearing) is to be fitted is forced in the heat ray fixing roller member for trying to drive it, the light transmissive base member tends to crack, and it is difficult to drive the heat ray fixing roller member. A primary portion of the first object of the invention is to solve the problem mentioned above and to make the heat ray fixing roller member to rotate without being subjected to damage of its light transmissive base member employing a glass member. In addition to the foregoing, another portion of the first object is to obtain conditions and structure of the roller for improving fixing capacity in the nip portion formed between the heat ray fixing roller member and a pressure rubber roller provided to face the heat ray fixing roller member.
Further, when a heat ray fixing roller of a fixing unit is being energized and in the initial stage of temperature rise of the heat ray fixing roller, heat on the surface of the heat ray fixing roller flows out to the light transmissive base member to be used to heat it. Therefore, if a pressure rubber roller provided to face the heat ray fixing roller is kept to be in contact with the heat ray fixing roller to rotate further, heat flows out to the pressure rubber roller, delaying temperature rise of the heat ray fixing roller, which is a problem. When the pressure rubber roller is warmed sufficiently, on the other hand, a temperature of the heat ray fixing roller can be raised quickly when it is energized. However, when the heat ray fixing roller is kept to be energized as the condition that the pressure rubber roller is not rotating when energizing of the heat ray fixing roller is suspended, the pressure rubber roller and the heat ray fixing roller are deteriorated, or deformed by temperature rise, which is a problem. In particular, temperature rise on a boundary surface between a heat ray absorbing layer of the heat ray fixing roller and a light transmissive elastic layer that is on the inside of the heat ray absorbing layer is so remarkable that the heat ray absorbing layer comes off the light transmissive elastic layer, which is also a problem.
The second object of the invention is to solve the problems stated above and thereby to provide a fixing unit wherein an outflow of heat from an energized heat ray fixing roller member to a pressure rubber roller is prevented, speedup for temperature rise of the heat ray fixing roller member is achieved, deterioration of the heat ray fixing roller member and the pressure rubber roller caused by contact between them is prevented, and exfoliation between the heat ray absorbing layer and the light transmissive elastic layer on their boundary surface is prevented.
The first object stated above can be attained by the following structures.
Structure (1)
A fixing unit for fixing a toner image formed on a transfer material on the transfer material under heat and pressure, wherein there is formed a roll-shaped heat ray fixing rotating member which has therein a heat ray emitting means that emits heat rays, and is provided with a cylindrical light transmissive base member that transmits heat rays, a light transmissive elastic layer composed of a light transmissive rubber layer on the outer side of the light transmissive base member, and a heat ray absorbing layer that is arranged on the outer side of the light transmissive elastic layer and absorbs heat rays, and a pressure rubber roller is provided to face the heat ray fixing roller member.
Structure (2)
The fixing unit according to Structure (1), wherein a rubber hardness of the pressure rubber roller is higher than that of the heat ray fixing roller member.
Structure (3)
The fixing unit according to Structure (1), wherein the pressure rubber roller is in a form of an inversed crown.
Structure (4)
The fixing unit according to Structure (1), wherein the fixing unit can move in the direction of an arc of the driving gear around the center of the driving gear for the pressure rubber roller.
Structure (5)
The fixing unit according to Structure (1), wherein a rubber hardness of the pressure rubber roller is 80xc2x0 or less.
Structure (6)
The fixing unit according to Structure (1), wherein an outside diameter of the pressure rubber roller is 60 mm or less, and a width of a nip formed by the pressure rubber roller and the heat ray fixing roller member is 10 mm or less.
Structure (7)
The fixing unit according to Structure (1), wherein an outside diameter of the pressure rubber roller is 60 mm or less, and a thickness of a rubber roller of the pressure rubber roller is 2 mm or more
Structure (8)
The fixing unit according to Structure (1), wherein the relationship of xcfx861 less than xcfx862 is satisfied when xcfx861 represents an outside diameter of the heat ray fixing roller member and xcfx862 represents an outside diameter of the pressure rubber roller.
The second object stated above can be attained by the following structures.
Structure (9)
A fixing unit for fixing a toner image formed on a transfer material on the transfer material under heat and pressure, wherein there is formed a roll-shaped heat ray fixing rotating member which has therein a heat ray emitting means that emits heat rays, and is provided with a cylindrical light transmissive base member that transmits heat rays, a light transmissive elastic layer located on the outer side of the light transmissive base member, and a heat ray absorbing layer that is arranged on the outer side of the light transmissive elastic layer and absorbs heat rays, and a pressure rubber roller is provided to face the heat ray fixing roller member, and when the heat ray fixing roller member is energized, rotation of the heat ray fixing roller member caused by contact with the pressure rubber roller is started when a temperature of the heat ray fixing roller member is raised up to the prescribed temperature or higher.
Structure (10)
The fixing unit according to Structure (9), wherein rotation of the heat ray fixing roller member is stopped after stop electricity for the heat ray fixing roller member is stopped.